An apparatus for a steam engine is known in the art, for example as disclosed in Japanese Patent Publication No. H7-180649, in which the energy is obtained by repeating vaporization and liquefaction of a fluid.
In the above apparatus, a volatile fluid is filled in a heating chamber, wherein the fluid is vaporized by heating the same and the vaporized fluid is introduced into a vertically arranged fluid pipe and guided to an upper portion of the fluid pipe. Then, the vaporized fluid is cooled and liquidized in a cooling chamber provided at the upper portion of the fluid pipe. The liquidized fluid returns to the heating chamber through the fluid pipe. A magnetic member is movably provided in the fluid pipe, so that a reciprocal movement of the magnetic member is generated in response to the movement of the fluid. An electric power is generated by producing electromotive force at a coil provided at an outside of the fluid pipe.
The applicant of the present invention has proposed a steam engine, as disclosed in Japanese Patent Publication No. 2004-84523 (which corresponds to U.S. Patent Publication No. 2004/0060294 A1). The steam engine is shown in FIG. 8.
The steam engine 500 comprises a loop pipe 502 having a circular pipe filled with the working fluid, a heating device 504 for heating the working fluid in the loop pipe 502, a cooling device 506 for cooling steam vaporized by the heating device 504, an output device 508, and a valve 520 for opening and closing the loop pipe 502.
The output device 508 comprises a cylinder 510, a piston 512 reciprocating in the cylinder 510, a moving member 514 connected at its one end to the piston 512, and a spring 516 connected to the other end of the moving member 514. The piston 512 moves in the cylinder 510 in a reciprocating manner according to pressure from the working fluid.
In the above steam engine 500, volumetric expansion of the working fluid occurs in the loop pipe 502, when the working fluid is heated and vaporized by the heating device 504. The vaporized steam heated by the heating device 504 moves upwardly toward the cooling device 506, at which the steam is cooled and liquidized. Then the volume of the working fluid in the loop pipe 502 is contracted. The piston 512 and the moving member 514 are reciprocated by change of liquid surface (self-excited vibration) as the pressure change due to the volumetric expansion and contraction of the working fluid in the loop pipe 502.
For example, a permanent magnet is disposed at the moving member 514 and a coil is faced to the permanent magnet, so that reciprocating piston 512 and the moving member 514 energize the coil.
As described above, in the steam engine 500 illustrated in FIG. 8, the vaporized steam heated at the heating device 504 moves upwardly toward the cooling device 506, at which the steam is cooled and liquidized.
Accordingly, in the loop pipe 502, the working fluid moves in one direction corresponding to the moving direction of the steam. In the steam engine 500, the velocity of the working fluid in the loop pipe 502 can be controlled by opening and closing of the valve 520. The control of the working fluid velocity can be used for controlling a time to exchange the heat of the working fluid in the loop pipe 502 with that of the cooling device 506 or the heating device 504.
It is, however, disadvantageous in the above steam engine 500 having one valve 520, in that heat efficiency is not sufficiently high. In this steam engine 500, for example, the movement of the working fluid located in the loop pipe 502 and at a place heated by the heating device 504 can be suppressed by closing the valve 520.
In this case, the vaporization of the working fluid heated by the heating device 504 is expedited, so that a larger volume of the vaporized steam is generated in the loop pipe 502 adjacent to the heating device 504.
Then, when the valve 520 is opened, the steam moves upwardly toward the cooling device 506 at once, as shown in FIG. 8. When the steam moves upwardly in such a manner, the working fluid below the steam likewise moves upwardly through the heating device 504, wherein the working fluid is heated but not to the vaporized temperature.
In the case that the working fluid passing through the heating device 504 is heated but not vaporized, the heat energy supplied to the working fluid, which passes through the heating device 504 as the liquid-phase working fluid, does not contribute to the volumetric expansion of the working fluid in the loop pipe 502, and thereby such energy can not be used for the reciprocal movement of the piston 512 and the moving member 514.
As above, a part of the heat energy is unnecessarily wasted in the above steam engine 500, the heat efficiency is decreased corresponding to such wasted heat energy.
The present inventors further considered a heating device shown in FIG. 9, which could be used as the heating device 504 shown in FIG. 8. As shown in FIG. 9, the heating device 504 has a fluid pipe 550, through which heated fluid, such as exhausted gas from an internal combustion engine of a vehicle, flows. The heating device 504 heats the working fluid in the loop pipe 502 by using the heat energy of the fluid passing through the fluid pipe 550. The fluid pipe 550 is constituted in such a manner that the heated fluid flowing in the fluid pipe 550 is contacted with a portion of the loop pipe 502 at which the working fluid is heated by receiving heat energy, and the heated fluid passes by the loop pipe 502.
In this case, the working fluid located at the heating portion receives the heat energy, the amount of which corresponds to the amount of the heat energy given to the heating portion from the heated fluid.
However, in such heating device 504, the amount of the heat energy given from the heated fluid passing through the fluid pipe 550 is small, so that the heat efficiency tends to be insufficient.
This problem will be further explained with reference to FIG. 10 in addition to FIG. 9. FIG. 10 shows relation between position and temperature of the heated fluid passing through the fluid pipe 550. As shown in FIG. 9, a reference “A” designates a position of the fluid pipe 550 at which the heated fluid is contacted with the loop pipe 502 for the first time, and a reference “B” designates a position of the fluid pipe 550 at which the heated fluid has passed by the loop pipe 502.
When the temperature of the position A is “TA” (Inlet Temperature) and the temperature of the position B is “TB” (outlet Temperature), relation between “TA” and “TB” is “TA”>“TB” (as shown in FIG. 10), because the heated fluid gives the heat energy to the heating portion while moving from the position A to the position B.
When the amount of the heated fluid passing through the fluid pipe 550 is “m” and a specific heat of the heated fluid is “Cp”, the amount of heat “Q” given to the heating portion of the loop pipe 502 from heated fluid is “m Cp (TA−TB)” at most, as shown in FIG. 10.
In FIG. 10, “Th” is a boiling temperature, “Tc” is a condensing temperature, and “Ta” is an air temperature. “TB” needs to be higher than “Th” (TB>Th) in order to properly vaporize the working fluid located at the heating portion by the energy of the heated fluid.
However, in the structure of the heating device shown in FIG. 9, the heated fluid having a higher temperature “TB” than the boiling temperature “Th” is emitted in such a manner that the heat energy of the heated fluid is not sufficiently used for heating the working fluid. Therefore, the heat efficiency tends to be insufficient.